1. Field of the Invention
The present invention relates to a channel selection voltage generator for a radio receiver, a television receiver or the like which is equipped with an automatic frequency control circuit for automatically maintaining a received signal frequency at a constant frequency.
2. Description of the Prior Art
The channel selection voltage generator for a radio receiver, a television receiver or the like which is equipped with an automatic frequency control circuit has been known, for example, by Japanese Pat. Appln. Post-Exam. Publn. No. 22125/68. In such a prior art apparatus, however, since the direction of sweep is limited to one direction, when it is desired to select a channel or a broadcasting station which is close to a channel or a broadcasting station currently being received but lies in a rearward frequency position with respect to the sweep direction, it is necessary to sequentially capture undesired stations and release the capture. Therefore, the channel selection operation is very troublesome.
Furthermore, since the prior art apparatus uses a continuously variable current source to control the received signal frequency, the apparatus is not suitable for digital control, and in particular it is not suitable for the channel selection voltage generator for a television receiver which is equipped with a discriminator for discriminating a picture carrier from a sound carrier to produce a digital discrimination signal.